


Bred Not Wed

by In_the_aroace_brigade



Category: Undertale (Video Game)
Genre: Alpha Alphys, Alpha Asgore, Alpha Gaster, Alpha Undyne, Alpha/Beta/Omega Dynamics, Alternate Universe - Underfell, Eventual Smut, Omega Sans, Other, Underfell Asgore, Underfell Papyrus, Underfell Sans, underfell gaster - Freeform
Language: English
Status: In-Progress
Published: 2016-11-02
Updated: 2016-11-02
Packaged: 2018-08-28 14:51:02
Rating: Explicit
Warnings: Rape/Non-Con
Chapters: 1
Words: 4,896
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8450611
Author URL: https://archiveofourown.org/users/In_the_aroace_brigade/pseuds/In_the_aroace_brigade
Summary: This was the universe of Underfell, where monsters killed each other for pleasure. But in this dynamic controlled world of Alphas/Betas/Omegas, they are brought to the brink of extinction by the killing off of the weaker Omegas. Now Omegas are less than 1% of the monster population and they are bred specifically to pull all of monsterdom back from the brink.But what if an Omega resists?





	

**Author's Note:**

> I haven't seen a A/B/O fic out there in undertale yet (doesn't mean it doesn't exist though) and the idea seemed so perfect for having dynamics included so here we are. I'm trying to keep the chapters longer so the next one will be posted when I have gotten to the point that I am prepared to do so at.
> 
> Tags will be updated as needed.
> 
> Update: The ages during Sans' flashback in chapter 1 were incorrect, I changed them to 17 and 15.

Sans sat at the desk in his room, reading one of the books provided. He had read all of them before but there was nothing else to do. He could have gone out into the sitting room with the others and catch the latest bit of gossip, as no one had anything better to do but to talk. He found himself not really caring about most of the going-ons of the monsters in his world, it wasn’t like he was going to be out there with them ever again. So he read, flipping through the pages once more in an effort to distract himself from his boredom. The handle to his door jiggled behind him and he turned around just in time to see one of the attendants step into the room.

“Omega, your next appointment is in 4 hours. Someone will be here shortly to help prepare you. Please remain in your quarters until they arrive.” They turned around and left without waiting for his acknowledgement, not that it would have mattered. He was an Omega, the rarest of the dynamics, and no matter how nicely they phrased it in 4 hours he would be bred once more. Sans wondered if it would take this time or if his magic would remain strong enough to keep this Alpha’s seed from planting within his womb.

Sans grinned wryly for a moment, content at least that he had disrupted the Omega Center staff’s plans for him thus far. He had never been successfully bred by anyone yet in the 2 years it had been since they had started his “appointments.” Everyone else here had been pregnant at least once, if not multiple times. Normally omegas were susceptible to being bred by any alpha, no matter how much they tried to fight against it. If they needed to, the staff even had permission to drug the omegas to make them more willing participants.

Sans was special, and he was thankful that there weren’t able to breed him either way. His low health of 1 HP made it so that the use of any drug on him during the breeding process could be very dangerous. He wouldn’t be able to tell a partner if something was going wrong, and even with all the machines that monitored every part of the process, that split second knowledge of knowing something was going wrong versus waiting for the alarms to start was vital in a case like his.

And as for alphas being able to overpower him, there were few that were up to the challenge. Sans had much more powerful magic than the normal omega, allowing him to resist submitting to the alphas presented before him. There had only been one alpha that he had submitted to like this, and it was during his first time when submitting was a given, even though no children were ever born of it. He hadn’t fought quite so hard that time, more in shock of the power that the alpha’s pheromones had on him. Every mating since that point he had known what to suspect, and could prepare himself to deal with the onslaught of emotions and hormones that it would entail. They had even begun holding meetings with several staff members to figure out how to take the fight out of him so he could be bred safely, but they had yet to come up with a solution.

He had been brought before the center’s director several months prior, the alpha rock monster peering at him over his glasses.

 

_**Begin Flashback** _

“Come in, Omega, and take a seat. I was hoping to talk to you about some of your behavior during the…sessions we have scheduled for you thus far.”

Sans slowly entered the room, trying not to show his displeasure of only being named by his dynamic. He knew it was center policy, to only address the omegas as such so that the staff didn’t form too much of an emotional attachment with their subjects. Even the files on every omega were just an identification number, with their real name mentioned only once on the intake sheet. Every report after that was by their ID number. Sans’ was 452631, a number he could roll off his tongue on demand. Not only did they all have to memorize it, but every number was branded onto their bodies. Once more, Sans was the exception; instead a moderately weighted silver cuff was engraved with his number and encircled his left wrist. It also contained a tracking chip so that the staff could find him at any time and a magic dampener that only affected his ability to teleport.

Sans sat down in one of the chairs in front of the director’s desk, trying to keep his pheromones under control so that the doctor wouldn’t be able to smell the fear on him. Every other dynamic was able to mask their outmost emotions with some success, but omegas “wore their heart on their sleeve.” Oftentimes when he had been less experienced at controlling his emotions the staff had been able to tell what he was feeling, even when he was unable to express it himself. Omegas reeked of these scents, originally for the purpose of letting their alpha know when they were in distress. Now that omegas were all locked together with the supposed purpose of keeping them safer, it just assisted the center staff in knowing when an omega was going to be difficult. Sans could thank his father Gaster for his incredible self-control. Growing up in the household with him allowed Sans plenty of practice in restraining himself. It just took a bit of retraining to direct it to his pheromones as well.

The director stood up and walked around the desk, choosing to perch on a corner in front of Sans. Sans scowled internally, the director was just trying to intimidate him with his size now. Everybody knew that size didn’t mean anything when it came to dynamics though. Alphys, a small lizard monster, had presented as a strong Alpha on her birthday just months before his. Meanwhile the former queen, arguably one of the largest monsters in the underground, was only a Beta, having fine skill in magic but not particularly powerful. That she was able to bear a child to their king was a miracle.

“Omega…” a scorning look flitted across his face before he could snuff it out, “Sans…” Now this was something new. He hadn’t heard his own name since the day of his first breeding, and at that point it had been a year since he had heard it last. It made him sit up a little straighter in his seat and actually look at the doctor before him. The nameplate on his desk declared him to be Dr. Mercury. The rock monster snapped his fingers in front of Sans’ face. “Pay attention, this is important.”

Sans shifted himself in the seat so that he could face the director head on. “Fine, what is it that you wanted to talk to me about.” Sans relished in seeing the director’s face darken at his tone. Outside where everyone else lived, that would be cause for a brawl. But since omegas were so precious, staff couldn’t lay a hand on them. Not that this meant that they didn’t have their own ways of punishing the residents. He was pretty sure his dinner ration tonight would be smaller than normal, enough to make him to be annoyed by hunger all night without hurting him.

“Omega,” so much for hearing his name, “why are you using your magic to prevent the breeding process to occur? The monsters we have brought to you have been perfectly suitable and specially chosen just for you. Why do you choose to fight the inevitable? And don’t give me that same nonsense about going out into the underground and choosing a mate for yourself. You know the rules, once a successful breeding takes place with a monster you cannot mate with them again so that we can increase the span of our population better. It wouldn’t do, say, if all we had were several skeleton monsters running about.” He wondered briefly about the director’s thoughts on what kind of monster he would choose as his mate. Skeletons were quite rare and the chances of him choosing one of them was highly unlikely. The director leaned closer to him, filling Sans’ field of vision and causing him to have to resist the instinct to cower before him and bare his neck in submission. Sans stared evenly back into the director’s eyes, forcing himself to breathe.

The doctor broke the staring contest by grabbing Sans’ head and holding him still. “H-hey, what are you-“ Sans said angrily. The doctor shushed him and for once Sans obeyed, unsure of what he was doing.

“This scar, how long have you had it?” The doctor inquired, his voice like gravel. Sans fidgeted with his hands in the chair, the doctor managing to bring up a sore point of childhood.

“Since I was, err, 7 or so. Doesn’t hurt or affect me so there wasn’t a point in healing up the wound, ya know?” Indeed, Gaster had been quite careful when he inflicted his son with this wound, making sure that Sans got a continuous supply of enough healing magic during its creation to ensure his son would still live at the end. As soon as he had finished creating it he had stood back to admire his work, pulling Sans’ head this way and that. Once he was satisfied he leaned down towards Sans and whispered in his ear “Remember, this is what happens to bad little boys who don’t obey their fathers. Now, don’t make me tell you again. Go get your brother and bring him to me so he can be punished as well.” Sans had risen, still shaking, and brought his younger brother Papyrus to his father. Gaster had then made Sans grab hold of Papyrus’ soul with this gravity magic and use it to hold his little brother in place while Gaster made a similar mark scratching through Papyrus’ eyesocket. Papyrus had taken it in stony silence, a vast difference to Sans’ hiccupped sobs, and as soon as it was done he had gone to his room for the rest of the night and locked himself away. The next morning Sans went to check on his little brother, and instead of finding the rough and tumble child from the day before, he found a neat room with all childish toys shoved into the closet or in a garbage bag by the door. That day had changed their lives forever.

Sans managed to tear himself out of the past as the director ran a finger down the crack, eliciting a grunt from Sans. “How did you get it?” The director inquired. Sans shifted in his seat “Fight with my bro, we both ended up marking each other.” The lie was well rehearsed, for no matter how rough this world was child abuse was still frowned upon. Their father had reminded them multiple times of his relationship to the king though, making sure they understood that he would discredit their claims and call them ungrateful liars if they so much as breathed a word of the truth. Neither of them doubted it, their father was perhaps as ruthless as the king himself, if not more so. Maybe that was why they had chosen each other to have the occasional romp with. The lack of suitable mates meant that many alphas turned to each other for some rough and ready sex, usually swapping out the roles so no one had to bottom all the time.

The director turned back to his desk and wrote a note down, Sans catching a glimpse of it. ‘Check patient 452631 for potential side effects relating to head wound, perhaps it is the cause for his unwilling attitude toward performing his duty for monsterdom.’ Oh great, more monsters prodding at him. At least it would give him a break from the breeding sessions; no breeding was permitted during periods of medical testing.

Dr. Mercury-no, the alpha, because if Sans would be stripped of his name so would he- walked around his desk and sat back down in his own chair, staring at Sans. “You know, I went to school with your father growing up. He was always very dedicated to his work, never stopping his attempts to free our kind from this hellhole. And yet, here I have his son, who could help bring monsters back from the brink of extinction, yet he fights every chance he is given to do his part. Makes me wonder how ungrateful you have to be to reject your place. Last I heard, your younger brother is just as devoted as your father and is growing into a fine young monster.”

Sans balled his fists inside the sleeves of his dress, glaring at the doctor. Luckily for him the doctor was lighting up a cigar and didn’t notice his ire. “So the question is, what are we going to do about you. We don’t want to take any drastic measures just yet, you are, after all, quite young and will be fertile for many years. But being the most magically strong omega here also makes your children coveted. We are going to run some tests and let you try a few more times. However, if that isn’t enough to let you conceive, then we have certain…tactics…that we can use to move things along.”

Sans visibly paled this time and the director sneered in triumph. “Oh, have you heard about our methods? Let me fill you in, just in case you don’t get the full scope. If we do it that way, you’ll have even less privacy than you do now. We would have at least one doctor in the room with you along with multiple partners. You’d be hooked up to a healing drip inserted into your soul, and will undergo a temporary bond to keep you passive during the process. After that they will all take turns with you until we are sure that it has been successful. You are no good to us as an omega unless you can be bred so risks with your health might have to be taken. If really necessary, we’ll pull the king himself in to break your defiance apart.” His eyes gleamed as he seemingly drank in the sight of Sans’ discomfort.

“But of course if you manage to become pregnant soon then we won’t have to do all that. Would be a shame, after all, to have to do it that way. Much less enjoyable for you, and alphas aren’t known for their patience when there is a tight little hole fluttering before them, especially once the omega starts begging to be filled up.”  The director sat back in satisfaction, the bulge in the front of his scrubs apparent even from Sans’ position across the desk. Sans decided that he better get out of here before the director decided to give it a try all of his own right there in his office.

“Thank you for updating me sir, but I think I should get back to my room.” Sans decided to play along for now, figuring it would give the director less of a reason to try something with him right then. He quickly rose from his seat and walked quickly to the door and opened it up to disappear into his room until he was dragged out for the next meal.

“Omega, we have one more monster scheduled for you before we try medical testing. I sincerely hope it takes this time.” Sans almost shuddered at the tone of the director’s voice.

“As you say, sir.” Sans closed the office door behind himself, having to keep himself from sprinting back to his room. Little did he know that the director was already on the phone with Gaster, discussing his son’s behavior and asking for suggestions. He was just focused on getting back to the bathroom before he threw up all the bile in his stomach.

_**End Flashback** _

 

Sans was startled by the knock on his door. He glanced at the clock and realized one of his 4 hours was gone, lost to his daydreams. “C-come in” He called out. Another attendant walked in, an alpha this time. Sans’ eyesockets widened slightly. He should have been expecting this, they wanted to grind on his magic with resisting this alpha so that by the time he got to the main event he would be too drained to fight. He had been lucky with having 3 months off for medical and psychiatric testing, but now they were going to take steps to make sure he would be impregnated. Sans hoped that this was all they were going to do this time and that he wouldn’t be expected to handle 3 sex-starved alphas at once.

The alpha attendant made a beckoning motion with his finger, calling Sans over to him. Sans took a deep breath and complied, reasoning that he needed to save his magic as much as possible without losing himself while being prepped. This was going to be the most difficult one yet. He yelped when the alpha picked him up and carried him out the door to the special washroom. Normally they were allowed to walk by themselves but Sans was sure that the attendant had been instructed to carry Sans and hold him as much as possible to make it harder for him to keep resisting. He wiggled in the alpha’s arms, using his arms to push against his burly chest, nearly growling at him

“I can walk you know! Unhand me at once!” The alpha rolled his eyes and shifted his grip on Sans so that he could grab both his arms with one hand, pinning them down against his body. In this position the only movement Sans could make was kicking his legs below the knee, and even then he was angled away from the alpha’s body so he couldn’t even hope to hit him. This position also put his soul closer to the alpha’s own, making the subtle dominance that the alpha emitted harder to resist. This alpha must have been well trained, perhaps even by the king himself. It worried Sans to think that the King himself may already be playing a bigger role in his breeding. Most alphas wouldn’t have been able to restrain themselves from punishing an omega for talking like that to them; this was why so many omegas had been killed off. Even more monsters of all three dynamics were hurt during retaliation for killing someone’s mate.

This monster also knew exactly how to restrain him while also forcing Sans to use subtle amounts of magic. The director had indeed been busy in the last 3 months to be obtaining and training an alpha of this skill level. Sans kicked a couple of times to show he wasn’t defeated before calming himself, trying to think of a distraction that would last through the bathing process. Nothing significant had really happened since his coming-of-age birthday party 3 years prior…no, there had to be something different to think about, anything!

Just then he felt a pulse from the alpha’s soul, a corresponding increase of pheromones filling the area. They had arrived at the washroom and the alpha was trying to keep him tame for the extended cleaning he was about to undergo. The alpha set Sans down on the table and began undressing him, leaving his bones bare. Wait, the alpha was going to bathe him as well? Normally a beta or another omega would do it, to relax the omega being bred. The director wasn’t pulling his punches with this, Sans was going to have to resist until he was left in the room, and then just begin again when his partner arrived. The alpha finished undressing him despite Sans’ token resistance and picked him back up, carrying him to the ornate tub. The deciding factor was when Sans saw the alpha pull a table with all the cleaning implements on it closer, including the little brushes that would be used on the holes in his sacrum. The memory beckoned and this time, Sans fell into it with open arms. Anything would be better than being mentally present while naked in a room with an alpha, an act that his body generally associated with one thing and one thing only.

 

_**Begin Flashback** _

Sans woke up on his 17th birthday to Gaster knocking harshly on his door. “Wake up Sans! Today is not the day to be lazy. It is time for you to start being more responsible, like your younger brother.”

Sans sat up in bed just as Gaster opened his door and barged in. “Sans, how can you live in this pig sty? This is disgusting, no wonder you always look like you are dressed like a slob.”

Gaster crossed quickly to his closet and through the doors open, examining the contents with a frown. He pulled out a wrinkled red collared button up shirt, black pants that appeared to have a mustard stain near the crotch, and a black vest that Sans had never seen before which meant that Gaster had put it in his closet at some point without his knowledge. Luckily Sans had learned not to hide anything important in there as a child so he wasn’t too worried about whatever Gaster may have found in his snooping.

Gaster pulled mostly white undershirt out of a drawer along with some clean underwear (Sans usually never bothered with it, was just another thing to wash) and a pair of socks. He threw the underclothes at Sans and whisked out the door with the shirt and pants. “I’d make you clean and iron these but I know you wouldn’t do it correctly. Ah, Papyrus, there you are. Done studying? Good, I’ll need help making your brother look like a halfway competent monster for when the king comes to the party today.”

Sans peered through the doorway, watching Gaster’s back disappear from his sight. Left behind was his younger brother Papyrus, who was still 2 months from turning 15 and entering advanced studies at the school, yet had already studied all of the textbooks and regularly sparred with an actual junior guardsman named Undyne. Papyrus stared at him a minute longer, the look in his eyes failing to give Sans any idea of what his thoughts might be. He walked away and Sans let his face drop into his hands. Sans was pretty sure all Papyrus saw in him was disappointment mixed with expectation, the same emotions everyone else had when it came to him. And since it was Papyrus, the disappointment was doubled for not being brave enough to stand up to their father all those years ago and very little expectations were had. Everyone expected him to become this powerful Alpha, his strong magic making up for his weak health. His father’s efforts of keeping him alive for all these years would be worth it finally and he could be proud of both of his sons.

Sans was pretty sure Papyrus knew the truth about him, that even if he would display as an alpha he would still be just as incompetent as before. Papyrus even fought a couple of his battles in the schoolyard, dismissing Sans as “weak and untested.” The only thing Sans could do was watch helplessly from the sideline as Papyrus battled, any attempts on his part to assist his brother brought with jeers of “Stay over there, you’ll just get in my way.” He sighed. His brother was so cool and he was….well, himself.

Sans jumped as a piece of fabric hit his skull, glancing up quickly. Papyrus stood in his doorway, already dressed in his own nice clothes for the party, arms crossed and glaring at Sans. “Don’t get any stains on it, numbskull, I want that back later.” Sans looked down at the bed and saw the black bow-tie that his brother had thrown at him lying beside him.

“Are you even awake yet? Ugh, I don’t know why Father is having a big party for you, we should have just kept this private so you wouldn’t embarrass us or yourself. Get ready soon or you’ll be in trouble, birthday or not.” Papyrus whirled around and left, presumably going downstairs to finish getting stuff set up. Gaster had made arrangements for Grillby to cater the event, but there was still plenty to prepare. The skirmishing ring had been one of the first things set up, where Sans would be tested until his dynamic showed. It was one of the few things that Papyrus hadn’t helped with, except to make sure the safety measures were in place. Even on this day, Papyrus was sure that he would have to rescue him. On dynamic day everyone presented stronger than normally, so that it could be absolutely clear what dynamic you were. Alphas were extremely powerful and volatile, even dusting another monster on occasion just on accident within their first month. Yet Papyrus didn’t believe that even with the help of the pheromones he could handle himself.

Sans looked down at himself in shame, his brother was right. He pulled himself out of bed and started to get dressed, noticing that someone (probably Papyrus) had brought his shirt and pants back up to him. At the very least he would try to make his brother proud of him, even it was just for today. He wanted Papyrus to be able to hold his head high for once when he looked at Sans, not that strange look that always seemed to be there when Sans caught Papyrus staring at him. He finished getting ready and hurried downstairs.

At the bottom of the steps, Papyrus stopped him and tsked, straightening his tie. “I don’t know why I thought you would be able to do this, you’ve never done it in your entire life.” He admonished. Sans tried to pull himself together and act like the alpha he was meant to be. “Yeah? Well excuse me for not wanting this death trap so tight. Someone catches this thing just right with their magic and I’ll end up choking.”

Papyrus stared at him. “If a monster is able to use this to choke you without harming the rest of you, then you haven’t done a very good job dodging. But maybe you are right, you need all the help you can get.” Papyrus moved to undo the bow-tie and Sans bravado faltered. He grasped Papyrus’ arm.

“Papyrus, just…put it on, okay? And…thanks for fixing it.” Sans waited a moment, looking into Papyrus’ eyes before glancing downward. Potential Alpha or not, his brother would always be stronger, cooler, braver….better….than he was. And that was how it should be. The seconds stretched longer and Sans was prepared to either go without the bow-tie or suffer Gaster’s disappointment by asking him to tie it when Papyrus pulled it back around his collar, tying it perfectly and still leaving Sans plenty of room to breathe.

“Don’t let anyone choke you with it, not like I can save you this time.” Papyrus stated, not even a hint of humor in his tone. Sans grunted, wanting to argue on his own behalf but not willing to expend the effort. Besides, it was hard to fight the truth, no matter how painful it was. He walked into the kitchen and sat down for breakfast. He wouldn’t be able to eat until the feast later after his dynamic showed and he had beaten his opponents. A plate was already prepared for him, full of good food to restore his energy reserves so he could last through the battles today. The only hope for him was if his dynamic presented quickly, there would be a lot fewer battles to fight and his stamina would be tested less. Gaster had made some liquid magic shots, things that he could drink quickly to restore his HP. It wasn’t traditional for the day but with his HP being as low as it was, exceptions had to be made.

“No good having him finally be useful if he just ends up dying right after” his father had stated a couple weeks ago, on the phone with someone. Sans had been eavesdropping on the conversation, but quickly stopped after that. He didn’t need to hear Gaster repeat everything that he already told him daily.

“Are you still not done? Sans, of all the mornings to spend daydreaming, this is not the one. Finish eating and go outside, monsters are already starting to gather.” Papyrus left the kitchen after scolding Sans, the front door closing behind him seconds later. Sans quickly gulped down the rest of what was on his plate and placed his dishes in the sink. He debated scrubbing them for once but realized he was only trying to delay the inevitable. Better to get it over with, he thought, and walked to the front door. Sans paused for a moment, took a deep breath, and walked outside into the crisp Snowdin air.

**Author's Note:**

> Author can be found at [accidentalfeelfest](http://accidentalfeelfest.tumblr.com/)


End file.
